Tag Archives: scientific method

6. How to Think Like a Scientist – The Custard Effect

How to think like a scientist for kidsCustard makes me puke. Violently. Specifically, chocolate custard. It’s my working hypothesis. I only have two data points, but that’s enough for me. Talking like a scientist, chocolate custard causes me to puke. The effect of me eating chocolate custard is: me puking. The arrow of cause ==> effect is one way. My need to puke did not cause me to eat chocolate custard.

Cause and effect. Every scientist studies causes and effects. The cause happens first, and then later there is an effect. Always. It’s so obvious that at times we forget. Cutting onions make me cry. Onions cause me to cry. The effect of cutting up onions is crying. And crying does not cause me to cut onions.

But, when I cut onions, I also always listen to the radio. These two things happen in pairs, but are completely unrelated.

This leads to one of the most important parts about thinking like a scientist: just because things happen together, does not mean that one necessarily caused the other, or that they are even related. Talking like a scientist, if things happen together it is called “correlation”. The biggest mistake people make is when they assume correlation also means causation. There is a correlation between the onions and listening to the radio, but there is no causation.

My favorite football team wins when I wear my lucky T-shirt. Did me wearing my “lucky T-shirt” cause (or even help) my team to win? Probably not. It’s more likely that I often wear that shirt on game days, and my team wins a lot. Correlation does not mean causation,

But sometimes it’s hard to know what’s going on. Thinking like a scientist, I observe:

Every night my dog barks at midnight.

How does my dog know its midnight? She even adjusts for daylight savings time! Is it magic? Does the clock cause my dog to bark?

No! After further investigation, it turns out that she barks every night at midnight because that’s when my neighbor lets his dog outside. Midnight and my dog barking have a correlation. But the cause of the barking is my neighbor’s dog. The time of night had nothing to do with it.

But sometimes it’s hard to know what causes what.

Suppose you find that all the kids who wear glasses also sit in the front row of your class. Does sitting up close cause their eye problems? Or are they sitting up close because they have eye problems?

The great thing about noticing correlations is that it leads to ideas for new hypotheses and experiments. The experiments will provide evidence either supporting causation or falsify the idea.

For instance, I could ask my neighbor to let his dog out at 10pm to see if my dog will bark early. Or I could do custard flavor experiments. Maybe I only puke on chocolate custard and I will love strawberry custard…

Fun Phineas Effect Facts
One of the most common grammar mistakes in the English language is confusing the words ‘effect’ and ‘affect’. Wow your English teachers by never mixing them up.

Effect with an E is a noun, meaning ” the result of”. What was the effect of me eating chocolate custard? Puke.

Affect with an A is a verb meaning “to influence or change”. Verbs are action words. Remember: A for action. Bad weather affects my mood. So does puking.

5. How to Think Like a Scientist – Controlling the Chocolate Chip Experiment

phineas_scientist001So I learned how to make my mother’s delicious chocolate chip cookies. But after a few batches I got bored, and like a scientist, started to experiment. My mom didn’t enjoy walnuts and rarely baked with them, but I love them. I decided to change her recipe and add walnuts to my mix. Success! My roommates and I thought they tasted great (except for my friend Tony, who is allergic to nuts).

But were the cookies better than the original recipe? It was hard to know. It was hard to remember exactly how the originals tasted. So, thinking like a scientist, the next time I divided the cookie dough into two bowls and added walnuts only to one of them. I baked both batches and we did a taste test. The walnut chocolate chip cookies were clearly superior. And Tony was happy.

Talking like a scientist, the batch of original recipe cookies was the control group and the walnut batch was test group. The original ingredients are called dependent variables and the walnuts the independent variable.

The mark of a good experiment is that it is a controlled experiment with only one independent variable. You only want to change one thing at a time so you know what you are testing. The control allows you to compare the results of the change.

It is fine to do an uncontrolled experiment (like I did with my first attempt at walnut cookies). But if the results are good, it should be followed by a controlled experiment to verify them.

Scientists use uncontrolled experiments to generate ideas for new hypotheses. Hey, what if I throw in some jalapeño peppers into the cookie dough?

Fun Phineas Fact
In medical research, controlled experiments are called clinical trials. Over the years, it has been shown that the results are more accurate if the patients don’t know whether they are in the control group or the test group. We call these blinded trials.

Think about doing a soda pop taste test with your friends. Then try it again putting a blindfold on them before they drink. Blinding prevents personal opinions from altering results.

It has been found that results are even more accurate when the doctors and nurses running the experiment don’t know which group is the control. We call these double blinded trials. A double blinded controlled trial is difficult and expensive to run, but is the gold standard of medical research.

The US Food & Drug Administration requires double blinded clinical trials be run before approving new medications.

4. How to Think Like a Scientist – The Chocolate Chip Experiment

phineas_scientist001My mother baked incredibly delicious chocolate chip cookies. A few times a year she would bake a huge batch of them. Every time they tasted the same… awesome. When I left for college I asked for the recipe. I am not a cook, but, heck, I can follow directions. How hard could it be?

Lets just say that my first attempt was a disaster. Instead of soft and gooey like hers, mine were hard and crunchy like bricks. And they tasted nasty. I tried again, this time being extremely careful to follow the recipe exactly. Same result! What was I doing wrong? It was time for me to think like a scientist to figure it out.

cookieThe next time I went home, I watched my mother very carefully as she baked them. I noticed four differences from my failed attempts:

  1. A missing ingredient. Cinnamon. Just a dash. Mom just shrugged when I asked her. Cooking is so natural to her, she didn’t even think about it. And she doesn’t even look at the recipe as she bakes.
  2. Speaking of dashes. The actual quantity of “a dash” varied from almost microscopic to a heaping spoonful depending on the spice.
  3. She used real butter instead of margarine as listed on the recipe.
  4. She removed cookies quickly from the baking sheet and placed them on a plate to cool. Apparently every cook knows this, so she didn’t write it down. I left mine on the pan to cool, and they continued to cook way too long, turning into crunchy bricks.

Armed with these insights, I attempted a third batch of cookies in my college apartment. And to the relief of my roommates, success! I nailed it perfectly.

My chocolate chip experience shows the importance of repeatability. My mom’s perfect cookies weren’t a fluke or accident, she could consistently make more any time. And just as important, I was able to get the same results when I used the same ingredients in the same quantities and followed the same steps.

Experiments following the scientific method must be repeatable by you and others. First, you as a scientist should be able to run the experiment many times and get consistent results. And just as important, other people, even your un-best friend, should be able to get similar results if they follow the same steps. If it’s not repeatable, it’s not believable. And if it’s not repeatable it’s not believable. (That was a joke).

As an experimental scientist, you must write down every detail about the experiment, even details you think are irrelevant. The day and time, the weather, the type of materials used, the location, exact quantities… everything that might affect the outcome. It would be terrible to get great results and not be able to recreate the experiment later. Think of my first batch of nasty cookies.

Here is my mom’s cookie recipe!

Rita’s Chocolate Chip Cookie Recipe (with my corrections)
Chef: Rita M. Kaufman


  • 1 cup + 2 tablespoons all-purpose flour
  • 1/2 teaspoon baking soda
  • 3/4 teaspoon kosher salt
  • 1/2 cup (1 stick) butter, softened
  • 1/4 cup granulated sugar
  • 1/2 cup brown sugar
  • 1/2 teaspoon vanilla extract
  • 1 large egg
  • 1 dash (1/8 tsp) cinnamon
  • 1 cup (6-oz. pkg.) Semi-Sweet Chocolate Morsel

PREHEAT oven to 375° F.

Line a baking sheet with parchment paper and spray lightly with nonstick cooking spray. Set aside.

COMBINE flour, baking soda and salt in small bowl. With an electric mixer on medium-high, or a wooden spoon, beat butter, granulated sugar, brown sugar and vanilla extract in large mixer bowl until creamy (about 20 minutes). Add eggs. Gradually beat in flour mixture. Stir in morsels. Drop by tablespoon onto baking sheet.

BAKE for 9 to 11 minutes or until golden brown. Cool on baking sheets for 1 minutes, move cookies to a plate to cool completely before serving (about 15 minutes).

Fun Phineas Fact
Where you live may affect how you bake. My mom’s recipe was written for cooking near the ocean. If you live at a higher altitude, like Colorado, you will need to make changes to get the same results. At high altitudes, water boils quicker, cookies bake slower, and dough rises faster. Check with a local cooking expert to make adjustments for your kitchen.


Website: Betty Crocker Baking Guide

Podcast: Skeptics Guide 5×5 episode 65.

3. How to Think Like a Scientist – Furry Cats and Fuzzy Theories

phineas_scientist001All this talk about hypotheses brings us around to theories. A theory is not just a guess. A theory is a group of related hypotheses that have been repeatedly validated by observation and survived all attempts to falsify. The strongest theories have hundreds of independent hypotheses with thousands of confirming experiments.

There is no minimum number of hypotheses or validations or falsification attempts needed to be a theory. There are just weaker and stronger theories. My cat color theory is really weak.

One hypothesis often leads to more. My hypothesis, that cats are either orange or grey, led me to another educated guess: a cat’s fur color was camouflage to help it hunt and hide.

This new hypothesis makes some bold predictions. If their fur was camouflage then:

  1. Wild orange cats should live in a place where the land is orange colored, maybe the prairie wheat fields of Kansas?
  2. Wild grey cats should live in grey places. Maybe the foggy Smokey Mountains of Tennessee?
  3. There might be green cats living in jungles and rain forests.
  4. There might even be white cats living in Canada near the North Pole.
  5. If we dig in lands that used to be orange or grey, we should find cat bones.

All five predictions can be tested. And the hypothesis can be falsified several ways. For example, if we find wild grey cats in Kansas, my guess is wrong.

Now lets assume that prediction No. 1 and No. 2 get verified. Wild orange cats are found in Kansas and grey ones in Tennessee. I now have a theory of cat fur colors. Cats are orange or grey. Their color is camouflage for where they lived in the wild.

My theory makes some predictions that still need to validated, and that’s OK, and of course it can be falsified at any time.

Scientists build on each other’s work and challenge one another all the time. One scientist might add to my theory with a new hypothesis: maybe black cats live in dark caves. Another scientist might propose a rival theory: a cat’s fur color is based on the color of food they eat. The experiments and observations will decide which, if any one, is right.

OK, let’s forget about cats for a minute and look at a real theory that truly changed the world.

Back in the 1800s scientists knew a bit about electricity and magnets and sunlight, three completely different topics. For instance, they knew that:

  • electricity (like lightning) could flow through copper wires
  • compass magnets pointed North
  • sunlight travelled roughly 186,000 miles per second, and
  • a prism could turn sunlight into a rainbow of colors.

They also knew two weird things but did not understand why:

  • flowing electricity caused nearby compass needles to point towards the wire, not North.
  • Moving magnets caused electricity to flow through nearby copper wires.

Then Scottish scientist James Maxwell figured out that electricity and magnetism also travelled at almost 186,000 miles per second similar to light. And then he had this crazy idea, an educated guess, that electricity and magnets and sunlight were really the same thing: electromagnetism. His crazy theory was eventually validated by thousands of experiments and survived hundreds of attempts to falsify it. It is one of the most successful theories ever made.

Electromagnetic Theory has led to the creation of electric generators, light bulbs, automobiles, telephones, computers, televisions, radios and lasers. It also inspired Albert Einstein to propose his theories of relativity.

Cat Named Tang(Please Note: The cat color idea discussed here is complete fiction. It is meant to illustrate how scientists think, not to be real science. Cats come in lots of colors and I don’t know why. A good scientist should always first research a topic thoroughly, perhaps in the library or on the Internet, before making “educated guesses”. But remember, I was just a little kid when I got my cat, Tang.)

Fun Phineas Facts
Some people criticize science saying “you don’t know anything for certain, you are constantly changing your mind”. This is true! But it is science’s biggest strength, not a flaw. Scientists are always questioning things, looking for better answers, and accepting the new evidence.

This also doesn’t mean that there are no facts in science. The theory of how gravity works does not change the fact that there is this thing called gravity and if you throw a water balloon up in the air, it’s going to come down and go splat. Electricity creates magnets; magnets create electricity. That’s a fact.

2. How to Think Like a Scientist – Colorful Cats

phineas_scientist001When i was a little kid, my family got a kitten. He was an orange tabby and I named him “Tang” after the powdered orange flavored breakfast beverage that NASA astronauts drank.

My cousins also had an orange cat and I had seen tigers at the Bronx Zoo, so I figured that all cats were orange. Imagine my shock when I saw my neighbor’s grey cat. What the heck? I guess I was wrong. After that I knew better, that cats were either orange or grey. Of course I was still very wrong, but I was closer to the truth.

NASA Tang AdvertisementIt’s okay to be wrong. Some of the best scientific discoveries are found that way. And though I didn’t realize it at the time, I was already thinking like a scientist, following the scientific method.

  1. I made an observation (orange cat)
  2. I made an educated guess (all cats are orange)
  3. I tested and verified the hypothesis (my cousin has an orange cat, and tigers are orange)
  4. Then I found that the hypothesis was false (oops! Some cats are grey)
  5. I revised my hypothesis (cats are either orange or grey)

Let’s examine these steps because they show how a guess becomes a hypothesis. A scientific hypothesis must be tentative, predictive, verifiable and falsifiable.

Yikes! What does that mean?

  • Tentative means I am not certain about my hypothesis, and I will change my mind if there is evidence that I was wrong.
  • Predictive means I am not just explaining what I have found. I am also making claims about future observations. The next cat anyone sees will be either orange or grey.
  • Verifiable means I can find more orange or grey cats. If I cannot, I got problems!
  • Falsifiable means that I can make an experiment to prove that my hypothesis is wrong. If I see a cat that is any other color besides orange or grey (maybe a black cat) then my hypothesis is wrong, it has been falsified.

It is impossible for me to check every cat in the world, so I can never completely prove my hypothesis. With each cat I find that is orange or grey, my hypothesis is more likely to be correct. But all I need is one black cat to make my hypothesis false.

Cat Named TangFun Phineas Fact
If an idea cannot be falsified, it is only an opinion. For example, “cats are weird” is not a hypothesis. Even if it is true, since it cannot be disproven it is not scientifically relevant. To be scientifically valid, a hypothesis must survive all attempts to falsify it. If I still believed that all cats are orange after I have seen a grey one, it would just be silly. But my opinion that orange kittens are cuter would still stand.

Website: Tang in Space

Video: 1970s Tang Commercial